Projected phase-space diagram showing V_LOS vs. major axis distance R from the centre of M 87, for all spectroscopically confirmed PNs (black asterisks). The major axis distance is given both in arcsec (bottom axis), and in kpc (top axis), where 73 pc = 1″. The dotted horizontal line shows M 87’s systemic velocity V_sys = 1275 km s^-1 from Sect. 3.2. The shaded area represents the region of the projected phase-space where the blue-shifted [OIII] 4959 Å emission line would fall below the wavelength of the blue edge of the FLAMES sort ordering filter HR08.